Ami losing my baby???????

hi guys. im currently 4 and a half weeks pregnant and yesterday afternoon i started bleeding. it wasn't loads and it lasted a few hours and i haven bled allnight (fingers crossed) what do u think the chances are that ill lose my baby? m so scared, ive had a miscarriage before about 5 yrs ago with my 1st baby, then i wen on to hav a healthy daughter who's now 3. only pain im getting is odd period type pains which i thought was normal in early pregnancy. im so scared.. thanx in dvance for any replys.